Exhaust muffler



Y INVENTOR. mm/

@fm o@ wm E RAWSON EXHAUST MUFFLER Filed April 2, 1954 Mq 13, 195s 2,834,425 ce Patented May 13, 1958 2,834,425 EXHAUST MUFFLER Emanuel Rawson, Chicago, Ill., assignor to Grand Sheet Metal Products Co., Melrose Park, Ill., a corporation of Illinois Application April 2, 1954, Serial No. 420,607 7 Claims. (Cl. 181-442) This invention relates to `an exhaust muler for use on automobiles, trucks and other automotive vehicles or for use in stationary gasoline internal combustion engmes.

The muffler forming the subject matter of the present invention is of the type having an elongated passage through which exhaust gases are directed, said elongated passage being defined by perforated metal. The perforations in the metal lead to sound absorbing fibrous material Vsuch as glass fiber or mineral Wool or the like. ln mufflers of this type, it has been found that the inert fibrous material such as glass ber is most edective acoustically when the material 'is in finely divided form. Thus for example in the case of glass fiber, the fine glass liber is most elfective. This fine fiber is also the most widely used and is least costly.

It has been found, however, that this line glass fiber deteriorates in the vicinity of the perforated sleeve through which exhaust gases pass. Whether the heat or the acoustic shock or the combination of the two is responsible is difficult to tell. However, the line glass fiber is pulverized, seeps through the metal perforations and is blown out of the exhaust. In the course of time, all of the glass fiber filling the space around the perforated sleeve disintegrates, disappears and renders the muliler inoperative as far as reducing noise is concerned.

I have found that this deleterious action may be eliminated by using a layer of coarse glass liber or other inert material in the region immediately surrounding" the perforated sleeve where the inert filler is exposed to acoustic shock and concussion, as well as heat. In the case of coarse glass liber, this material comes `as a coarse mat and is more expensive than the fine glass fiber and is acoustically not as satisfactory; Therefore, a relatively thin layer of such glass ber mat is used to surround the perforated sleeve through which the exhaust gases pass. Disposed around the coarse glass liber mat is the ccnventional filling of fine glass liber.

The coarse glass liber mat has more body than the line glass liber and resembles a felted material in having strands crossing each other at all angles. The line glass is conventional glass wool and resembles soft cotton batting.

Instead of coarse glass liber, it is possible to use other inert material which can withstand the acoustic shock and heat of the exhaust. Such other material may, for example, be asbestos, magnesia, or other brous material capable of withstanding the intense heat and strong enough or soft enough to withstand the acoustic shock.

In order that the invention may be understood, it will now be explained in connection with the drawings wherein an exemplary embodiment is shown, it being understood that variations are possible without departing from the scope of the invention except as dened by the appended claims.

Referring to the drawing,

Figure 1 is a longitudinal sectional view of an exhaust muffler embodying the present invention.

Figure. 2 is an end view along line 2 2 of Figure l.

Figure 3 is a section along line 3-3 of Figure 1.

Figure 4 is a section along line 4-4 of Figure l.

The exhaust muffler embodying the present invention comprises three nested elongated tubular members 10, 11 and 12. Member 10, which is the core, consists of a perforated metal pipe, the metal being of sheet iron or sheet steel as desired. As a rule, tubular member 10 may be formed in a manner generally resembling a stove pipe in having the meeting edges of a llat sheet curled or otherwise suitably attached to maintain the member in its round condition. It is understood that any of the three nested members .may depart from a round shape. However the circular cross section as illustrated is generally preferred for simplicity. Tubular core 10 has ends 14 and 15.

Surrounding core 10 is intermediate perforated tubular member 11 having ends 17 and 18 respectively. Intermediate tubular member 11 is also formed of perforated sheet iron or sheet `steel and may conveniently be formed as illustrated in Figures 3 and 4 'of four quadrant portions 19 to 22 inclusive. Each quadrant portion has the longitudinal edge bent outwardly so that adjacent edges form outwardly extending flanges 24. The quadrant portion-s may be spot welded at the outwardly extending flanges to maintain the generally tubular character of intermediate member 11. As lan example, core 1l) and intermediate tubular member 11 may be made of 22 gauge sheet iron, the material having AG holes with the centers of the holes spaced 1/8 apart. The holes are staggered so that the sheet metal has substantial strength.

It will be noted that ends 14 and 15 of core member 10 stop' short of ends 17 and 18 of intermediate tubular member 11. Core member lll is maintained in centered relation with respect to intermediate tubular member 11 by annular trough-shaped retainers 26 and 2'7. These retainers may be spot welded to the outside and inside parts of tubular members 10 and 11 respectively.

Disposed around intermediate tubular member 11 is outer shell l2 consisting of solid sheet iron or sheet steel as desired. Outer shell 12 has ends 29 and 3) engaged by annular support members 32 and 33 respectively. Support members 32 `and 33 are shaped to resemble a wave extending in a circular pattern, having crest 34 and trough 35 in support member 32 and crest 35 and trough 37 in support member 33. Ends 29 and Sil of shell 12` and the perforated portions of annular support members 32 and 33 are crimped as shown to provide a sturdy construction.

rIhe annular support members are so disposedl that the troughs engage ends 17 and 18 of intermediate tubular member l1 to retain the same longitudinally within shell 12. Outwardly extending flanges 24 formed in intermediate tubular member 11 are designed to it within the inside of shell 12 and thus maintain the intermediate tubular member centered within the shell. It will bey noted that annular space 39 between core i@ and intermediate tubular member 11 is both shorter axially ofthe muler and greater radially of the mufler compared to the region between intermediate tubular member l1 and shell 12.

Between annular support 32 and annular troughshaped retainer 26 is open region 4l, this region being within intermediate tubular member 11. Between annular supf port member 33 and annular trough-shaped retainer 27l is region 42, also within intermediate member l1. Region 41 is preferably substantially longer in extent than region 42.

Annular support member 32 has an intake coupling sleeve 44 welded or suitably attached to the inner llange of the support. Similarly, annular support 33 has discharge coupling sleeve 45 attached to the inner flange part thereof. The two coupling sleeves may be slotted asv shown and may 'be disposed out of line with the axis of silencing purposes. In accordance with this invention,

inner layer 47 of this mass of material consists of relatively coarse glass fiber mat. This forms a layer immediately around the outer surface of core 10.

The thickness of layer 47 may vary depending upon the distance between the outer surface of inner core lil and the inner surface of intermediate sleeve 11. In general, however, the thickness of layer 47 may be of the order of about 1/16 of an inch. The actual thickness of layer 47 will depend in some measure upon how tightly the glass fibers are compressed into the space between the core and the sleeve. Another factor which will determine the thickness of fiber mat 47 will be the size available in the market.

In comparison to the thickness of coarse fiber mat 47, the remainder of the space within intermediate sleeve 11, lled by fine glass fibers 48,.will be large. As a rule, the coarse glass fiber mat comes in sheets having a number of layers packed together. The fine glass fiber comes in bats `but has less body than the glass mat.

Thus as an example of a muliier, the space between core and intermediate sleeve 11 has a dimension of about 1" with a sheet of coarse glass fiber mat disposed around the outside surface of inner core 10 and the remainder of the space being packed with glass wool or fine glass fiber. Inner core 10 in such a muffler may have a diameter of the Order of about l/z" while intermediate member 11 may have a diameter of the order of about 31A" with outer member 12 havingv a diameter of about 3%". The overall length of the mufer excluding the intake and outlet connections may range anywhere as from about 17" to about 30 depending upon the engine size and various other factors. These dimensions are merely exemplary and will vary depending upon the size of the engine and the desired exhausting effects.

The length of region 41 will generally be substantially greater than the length of region 42 but the respective lengths may vary within wide limits without departure from the scope of the present invention.

It will be noted that the inlet and outlet coupling sleeves have diameters at the annular supports somewhat larger than the diameter of core 10.

Instead of glass wool forming portion 48 of the muf fier packing, other inert wools such as asbestos or the like may be used. The coarse glass fiber mat forming layer 47, however, is preferred above all other known materials and is highly effective.

What is claimed is:

1. A muier for automobile engines comprising three nested elongated tubular metal members laterally spaced from each other along substantially all of their respective opposed surfaces, the two inner members thereof being perforated, means for maintaining said membersin generally symmetrical relation with respect to each other, a layer of relatively coarse glass fiber mat disposed immediately around the outer surface of said innermost member and additional fibrous inert material disposed over the rst named fiber mat, said additional material being substantially finer than the coarse glass fiber and normally being subject to rapid deterioration when used directly around said innermost member, the ber mat being strong enough to resist deterioration due to exposure to the exhaust gases.

2. An automobile exhaust mufiier comprising three nested elongated tubular metal members laterally spaced from each other along substantially all of their respective opposed surfaces, the two inner members being perforated, the innermost member stopping Short of the remaining two members at both ends of Isaid innermost member, means for maintaining said members in generally sym- ,4 metrical relation `with respect to each other, a layer of relatively coarse lglass fiber disposed immediately around the outer surface of said innermost member and additional fibrous inert material disposed around said first named coarse glass fiber layer, said additional material being substantially finer than the coarse glass fiber and normally being subject to rapid deterioration when used directly around said innermost member, said two layers filling the space between the two perforated members.

3. An automobile exhaust muliier comprising three nested elongated tubular metal members laterally spaced from each other along substantially all of their respective opposed surfaces, the two outer members having substantially the same length while the innermost member is substantially shorter than the remaining two outer members, the two inner members being perforated, means for maintaining said members in generally symmetrical relation with respect to `each other, the innermost member being disposed so that one end thereof is farther from the co1- responding one end of the remaining two members than theother end of said innermost member is from the other end of the remaining two members, a thin layer of coarse glass fiber disposed immediately around the outer surface of said innermost member, additional fibrous inert material disposed around said first named layer and filling the space within said intermediate member, annular supports carried jointly by the two outer members at their respective `ends and inlet and outlet coupling sleeves carried by said annular supports.'

4. An automobile exhaust muffler comprising three nested elongated tubular metal members, the outermost .member being of solid material and shaped to form a generally circular pipe, an intermediate member of perforated metal, said intermediate member having a length substantially the same as the outer member and having externallyl directed anges for fitting against the inside surface of the outermost member so that the intermediate member may be maintained in predetermined relation within the outermost member, the innermost member being of perforated sheet metal and having a length substantially shorter than the remaining other members, said innermost member having a generally circular cross section, annular members at both ends'of the innermost member for maintaining the innermost member in generally centered relation within the intermediate member, a layer of coarse glass fiber mat disposed around the outer surface of the innermost member, glass wool disposed around lsaid first mentioned glass layer, all of said glass being disposed between the two perforated members and between the two annular retaining members.

5. The construction according to claim 4 wherein annular support members are provided at the two ends of the two outer members, said annular support members retaining the intermediate member in position, said annular support members being adapted to have connected thereto inlet and outlet members.

y6. The construction according to claim 5 wherein said annular support members have inlet and outlet sleeves connected thereto.

7. The construction according to claim 4 wherein the innermost member is disposed substantially farther from one end of the two outer members than from the other end of the two outer members, said one end forming the inlet for the exhaust muffler.

References Cited in the file of this patent UNITED STATES PATENTS Y,

1,878,424 Oldberg Sept. 20, 1932 1,990,837 Morgenstern Feb. 12, 1935 2,059,487 Peik Nov. 3, 1936 FOREIGN PATENTS i i 482,809 Great Britain Apr. 5, 1938 498,533 GreatfBritain Jan. l0, 1939 704,329 Great Britain Feb.y 17, 19,54 

